As dogs age, often the cartilage surface of their joints begins to thin and die off. This process releases enzymes which causes inflammation of the joint and the loss of joint fluid resulting in on-going pain and stiffness. There are many supplements on the market that I'm not going to get into right now. That would be something you should discuss with your holistic veterinarian. I will recommend fish oil as the single most important supplement proven to provide the omega-3 fatty that help reduce inflammation.
Another great thing for your dog would be giving it massages. You can watch many of the YouTube videos on how to stimulate blood flow. Also, warm compresses on the joints can be very soothing. Of course you'll want to reduce the amount of exercise but not limit it. Swimming is a wonderful exercise that can help as long as it's not overdone. It's a good idea to consult your veterinarian on which would be the best forms of exercise for your dog but really keep in mind low impact. A light walk and swimming are really the best ways to prevent obesity and get the blood circulating to those stiff joints.
It's also important to keep down your dog's weight. Another one of the many benefits of salmon oil is its ability to help with weight loss and maintaining a healthy weight. You should never be able to see the dog's ribs but always be able to feel them. This is the easy guide for weight, knowing that your dog is at the right weight. Salmon oil is beneficial no matter what type of diet you're feeding. If you're feeding kibble, just pour the salmon oil in a teaspoon and mix it in with the kibble and do the same on raw food if that's what you're feeding. Studies have been published proving using fish oil as a treatment for canine arthritis does improve the symptoms.
Lastly, I would recommend pain relief. You would have to talk to your vet about that, or your holistic veterinarian. There are natural anti-inflammatories and other alternative therapies. Aside from the massage, some people have had success with acupuncture for arthritis. I really like a product called Traumacare. It is homeopathic and can be found at your local health food store